The present invention relates to an image processing apparatus and method capable of adding information to image data.
There are many cases (such as in the prevention of forgeries) in which additional information should be added to basic image data but which is imperceptible to human eyes. Conventionally, when additional information is added and multiplexed to image data of an original, the original image data deteriorates considerably. To solve the above problem, U.S. Pat. No. 5,257,119, which utilizes the visual characteristic of human eyes, adds the additional information to a yellow component of an original multicolor image. The added information will be imperceptible due to the characteristics of the human eye.
However, there are cases in which the added information is needed to be extracted or restored. In order to be able to extract and decode the added information from an output image generated by conventional techniques, additional data with a considerably large value needs to be added and modulated in the multiplexing processing. The modulation causes the image quality to deteriorate, while it provides the advantage that the added information is imperceptible to human eyes.
Since the conventional technique utilizes a particular color which is difficult to discriminate by human eyes, the multiplexing process is practically applied only to a multi-color image, but not to a monochromatic image.
Furthermore, in the case where the information adding processing is applied to a multi-color image and then the output image is post-processed with such a color conversion process, the added information is converted to a color which is of high perceptibility. Thus, it becomes unpractical.
Furthermore, the added information is easily read by a third person, and this is inconvenient when the added information is confidential.
Still further, there are additional image pattern which cannot be added and/or separated with the conventional techniques. Thus, it is impossible to provide a stable multiplexing or addition operation.